A vehicle is equipped with a variety of notification apparatuses for notifying a driver of a variety of types of information on driving. In recent years, in particular, studies have been undertaken to develop technologies for displaying a variety of types of information on a windshield. Display technologies using a projected virtual image or using a pattern have been known, one example of which is disclosed in Japanese Patent Application Laid-Open Publication No. 2006-8089 (JP 2006-8089 A).
In the in-vehicle information display apparatus disclosed in JP 2006-8089 A, a pattern containing information is provided on a windshield. The pattern is provided on the windshield by being printed or engraved on the glass or by a film being inserted in the glass. The information expressed in the pattern includes a substantially trapezoidal picture drawn along a driving lane, and helps the driver to travel straight forward. The driver can readily drive the vehicle straight forward by maneuvering the vehicle in such a way that the trapezoidal pattern always follows the driving lane viewed from a passenger compartment through the windshield.
The in-vehicle information display apparatus described above, however, only relates to a technology in which a trapezoidal pattern is simply provided on the windshield. The driver is only able to visually recognize the pattern as a flat displayed object. To visually notify the driver of information in a more appropriate, quicker manner, it is preferable to enhance the visibility of the pattern.
Further, when the driver is driving a vehicle while looking at a distant scene from the passenger compartment through the windshield, the driver's eyes focus on a point far away from the windshield. In this case, the pattern provided on the windshield is also within the sight of the driver. The portion of the pattern within the periphery of the sight is, however, multiplied due to binocular parallax of the driver in some cases, which is then visually superimposed in the horizontal direction. The driver feels uncomfortable with the thus displayed pattern. To visually notify the driver of information in a quicker and more appropriate manner, it is preferable to eliminate the uncomfortable feeling with the displayed pattern and enhance the visibility of the pattern.
The above discussion holds true for a method for displaying a virtual image containing information on a windshield.